Department of Physics and Astronomy, Katholieke Universiteit Leuven, Celestijnenlaan 200D, Leuven, 3001, Belgium.
Macromol Rapid Commun. 2011 Jun 1;32(11):844-8. doi: 10.1002/marc.201100029. Epub 2011 Apr 20.
We developed an experimental method for the determination of the tracer diffusivity D(tr) in ultrathin polymer films, and the changes in the segmental mobility of tracer molecules while they diffuse through matrices of different thickness and get adsorbed onto a target substrate. D(tr) starts decreasing already at 120-150 nm and drops to 1% of its bulk value in films as thin as 7.5 nm. We discuss the results highlighting a strong decoupling between the reduction in mass transport at the nanoscale and the increase in the glass transition temperature determined via capacitive dilatometry together with a breakdown of the Stokes-Einstein relation between orientational and translational degrees of freedom.
我们开发了一种用于测定超薄聚合物薄膜中示踪剂扩散系数 D(tr)的实验方法，以及示踪分子在扩散通过不同厚度的基质并被吸附到目标基底时的分子段运动性的变化。D(tr)在 120-150nm 时就开始下降，在厚度只有 7.5nm 的薄膜中下降到其本体值的 1%。我们讨论了这些结果，强调了在纳米尺度上质量传递的减少与通过电容膨胀计确定的玻璃化转变温度的增加之间的强解耦，以及取向和平移自由度之间的斯托克斯-爱因斯坦关系的破裂。
